Inflammation and tissue damage

Friday, October 04, 2013, 15:30 - 17:00

Secretory products of B cells of patients with relapsing remitting multiple sclerosis are cytotoxic for neurons in vitro

R. Lisak, L. Nedelkoska, B. Bealmear, J. Benjamins, H. Touil, R. Li, H. Misirliyan, B. Fan, A. Bar-Or (Detroit, US; Montreal, CA)Objective: To determine if supernatants (Sup) from B cells of patients with multiple sclerosis (MS) and normal controls (NC) were cytotoxic for neurons in vitro.
Background: B cells are increasingly recognized as playing important roles in the pathogenesis of MS, some of which are unrelated to maturation into autoantibody secreting plasmablasts and plasma cells. B cells can present antigen, have immunoregulatory capacity and secrete cytokines. We previously reported that Sup from B cells from patients with relapsing remitting MS (RRMS) but not from normal individuals (NC) were cytotoxic for oligodendrocytes (OL) but not astrocytes or microglia in vitro. The cytotoxic effect of the Sup was not related to presence of absence of IgM or IgG and was not dependent on complement activation. We hypothesized that B cell secretory products would also be cytotoxic for central nervous system (CNS) neurons. Methods: Neurons were isolated from CNS of neonatal rats as previously reported. Cultures consisted of 85% neurons, 10% astrocytes, 5% microglia with no OL or their precursors. B cells were obtained from the blood of 7 patients with RRMS and 8 NC, cultured for 48-96 hours in the absence of any additional stimulation and the Sup harvested and frozen until testing. Thawed Sup from B cell cultures were then diluted 1:4 with neuronal culture medium and neuronal cultures were treated for 72 hours. Cell death was determined by uptake of trypan blue.
Results: Media alone (non-conditioned B cell culture medium diluted 1:4 with neuronal culture medium) was non-toxic for neurons. B cell Sup from NC induced neuronal death of 8.4% (range 0-29%; S.E.M. ± 3.2) whereas Sup from MS induced neuronal death of 46.6% (range 37-63%; S.E.M. ± 3.6), with the difference significant at p<0.001. There was no observed toxicity for the few astrocytes or microglia in the cultures.
Conclusion: Sup of B cells of all MS and a few NC induce killing of neurons, with a greater effect seen with Sup from MS. Thus B cells might contribute to pathogenesis of MS via secretion of molecules that damage and kill neurons. B cells found in the atypical germinal follicle-like structures in the meninges of patients with early RRMS and secondary progressive MS (SPMS) could be particularly important in mediating demyelination and neuronal damage in the type III subpial cortical lesions seen in such patients.

R Lisak has received research support from Teva Neuroscience, Questcor, Avanir, Novartis, Sanofi Aventis, Genentech and Biogen/Idec. He has received honoraria from Teva, Bayer Health, Questcor and Avanir
L Nedelkoska has nothing to disclose
B Bealmear has nothing to disclose
J Benjamins has received research support from Teva,Questcor and Avanir
H Touil has nothing to disclose
R Li has nothing to disclose
H Misirliyan has nothing to disclose
B Fan has nothing to disclose
A Bar-Or has received research support from Teva Neuroscience, Bayhill Therapeutics, Biogen/Idec, Genentech and Merck-Serono. he has received honoraria from Bayer, Bayhill Therapeutics, Biogen/Idec, Diogenix, Eil Lilly, Genentech, GSK, Guthy-Jackson, Merck Serono, Novartis, Ono Pharmacia, Roche, Sanofi Aventis, Teva Neuroscience and Wyeth
The study was funded by the Parker Webber Chair in Neurology Endowment (DMC Foundation/Wayne State University), the Mary Parker Neuroscience Fund (DMC Foundation)